在"HHWM下为什么会出现未格式化的块"这篇文章里给我提了两个问题，我也作了回答。
但感觉还是回答的不够清晰，不知道Kostas明白没有，我这里还是直白的回答一下吧。
1、Is the L3 bitmap block at the beginning within the segment header?
Answer: No. But the segment header can be viewed as the first L3 BMB present in an ASSM segment. In ASSM segments, BMBs (including L1、L2 and L3) are placed ahead of the segment header for the first extent (extent 0). If BMBs are required for subsequent extents, they exist as the first blocks in the extent.
2、Where is the extent map header located?
Answer: You can track the extent map block by using ktemh struct in segment header block. Extent map blocks are extent maps that overflow when the extent map area in the segment header block is not large enough to describe all extents that are used by a segment. Entries in an extent map block have the same format as the extent map in the segment header.
An extent map block is always allocated as the first block in the first extent in FLM segments. Each extent map block is pointed to by the previous extent map block. The head of the linked list is in the segment header block.
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